Re: [PATCH v8 00/26] APEI in_nmi() rework and SDEI wire-up

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

On Monday, February 11, 2019 7:35:03 PM CET James Morse wrote:
> Hi Rafael,
> 
> On 11/02/2019 11:05, Rafael J. Wysocki wrote:
> > On Fri, Feb 8, 2019 at 3:13 PM James Morse <james.morse@arm.com> wrote:
> >> On 08/02/2019 11:40, Rafael J. Wysocki wrote:
> >>> On Tuesday, January 29, 2019 7:48:36 PM CET James Morse wrote:
> >>>> This series aims to wire-up arm64's fancy new software-NMI notifications
> >>>> for firmware-first RAS. These need to use the estatus-queue, which is
> >>>> also needed for notifications via emulated-SError. All of these
> >>>> things take the 'in_nmi()' path through ghes_copy_tofrom_phys(), and
> >>>> so will deadlock if they can interact, which they might.
> >>
> >>>> Known issues:
> >>>>  * ghes_copy_tofrom_phys() already takes a lock in NMI context, this
> >>>>    series moves that around, and makes sure we never try to take the
> >>>>    same lock from different NMIlike notifications. Since the switch to
> >>>>    queued spinlocks it looks like the kernel can only be 4 context's
> >>>>    deep in spinlock, which arm64 could exceed as it doesn't have a
> >>>>    single architected NMI. This would be fixed by dropping back to
> >>>>    test-and-set when the nesting gets too deep:
> >>>>  lore.kernel.org/r/1548215351-18896-1-git-send-email-longman@redhat.com
> >>>>
> >>>> * Taking an NMI from a KVM guest on arm64 with VHE leaves HCR_EL2.TGE
> >>>>   clear, meaning AT and TLBI point at the guest, and PAN/UAO are squiffy.
> >>>>   Only TLBI matters for APEI, and this is fixed by Julien's patch:
> >>>>  http://lore.kernel.org/r/1548084825-8803-2-git-send-email-julien.thierry@arm.com
> >>>>
> >>>> * Linux ignores the physical address mask, meaning it doesn't call
> >>>>   memory_failure() on all the affected pages if firmware or hypervisor
> >>>>   believe in a different page size. Easy to hit on arm64, (easy to fix too,
> >>>>   it just conflicts with this series)
> >>
> >>
> >>>> James Morse (26):
> >>>>   ACPI / APEI: Don't wait to serialise with oops messages when
> >>>>     panic()ing
> >>>>   ACPI / APEI: Remove silent flag from ghes_read_estatus()
> >>>>   ACPI / APEI: Switch estatus pool to use vmalloc memory
> >>>>   ACPI / APEI: Make hest.c manage the estatus memory pool
> >>>>   ACPI / APEI: Make estatus pool allocation a static size
> >>>>   ACPI / APEI: Don't store CPER records physical address in struct ghes
> >>>>   ACPI / APEI: Remove spurious GHES_TO_CLEAR check
> >>>>   ACPI / APEI: Don't update struct ghes' flags in read/clear estatus
> >>>>   ACPI / APEI: Generalise the estatus queue's notify code
> >>>>   ACPI / APEI: Don't allow ghes_ack_error() to mask earlier errors
> >>>>   ACPI / APEI: Move NOTIFY_SEA between the estatus-queue and NOTIFY_NMI
> >>>>   ACPI / APEI: Switch NOTIFY_SEA to use the estatus queue
> >>>>   KVM: arm/arm64: Add kvm_ras.h to collect kvm specific RAS plumbing
> >>>>   arm64: KVM/mm: Move SEA handling behind a single 'claim' interface
> >>>>   ACPI / APEI: Move locking to the notification helper
> >>>>   ACPI / APEI: Let the notification helper specify the fixmap slot
> >>>>   ACPI / APEI: Pass ghes and estatus separately to avoid a later copy
> >>>>   ACPI / APEI: Make GHES estatus header validation more user friendly
> >>>>   ACPI / APEI: Split ghes_read_estatus() to allow a peek at the CPER
> >>>>     length
> >>>>   ACPI / APEI: Only use queued estatus entry during
> >>>>     in_nmi_queue_one_entry()
> >>>>   ACPI / APEI: Use separate fixmap pages for arm64 NMI-like
> >>>>     notifications
> >>>>   mm/memory-failure: Add memory_failure_queue_kick()
> >>>>   ACPI / APEI: Kick the memory_failure() queue for synchronous errors
> >>>>   arm64: acpi: Make apei_claim_sea() synchronise with APEI's irq work
> >>>>   firmware: arm_sdei: Add ACPI GHES registration helper
> >>>>   ACPI / APEI: Add support for the SDEI GHES Notification type
> >>
> >>
> >>> I can apply patches in this series up to and including patch [21/26].
> >>>
> >>> Do you want me to do that?
> >>
> >> 9-12, 17-19, 21 are missing any review/ack tags, so I wouldn't ask, but as
> >> you're offering, yes please!
> >>
> >>
> >>> Patch [22/26] requires an ACK from mm people.
> >>>
> >>> Patch [23/26] has a problem that randconfig can generate a configuration
> >>> in which memory_failure_queue_kick() is not present, so it is necessary
> >>> to add a CONFIG_MEMORY_FAILURE dependency somewhere for things to
> >>> work (or define an empty stub for that function in case the symbol is
> >>> not set).
> >>
> >> Damn-it! Thanks, I was just trying to work that report out...
> >>
> >>
> >>> If patches [24-26/26] don't depend on the previous two, I can try to
> >>> apply them either, so please let me know.
> >>
> >> 22-24 depend on each other. Merging 24 without the other two is no-improvement,
> >> so I'd like them to be kept together.
> >>
> >> 25-26 don't depend on 22-24, but came later so that they weren't affected by the
> >> same race.
> >> (note to self: describe that in the cover letter next time.)
> >>
> >>
> >> If I apply the tag's and Boris' changes and post a tested v9 as 1-21, 25-26, is
> >> that easier, or does it cause extra work?
> > 
> > Actually, I went ahead and applied them, since I had the 1-21 ready anyway.
> 
> > I applied the Boris' fixups manually which led to a bit of rebasing,
> > so please check my linux-next branch.
> 
> Looks okay to me, and I ran your branch through the POLL/SEA/SDEI tests I've
> been doing for each version so far.

Thanks for the confirmation!


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